Coordination‐Engineered Cu Single Atom on N‐Doped Carbon Nanosheets for Highly‐Efficient Photocatalytic CO 2 Reduction to CH 4

ABSTRACT Photocatalytic CO 2 conversion offers sustainable catalytic pathway for solar fuel production and CO 2 mitigation. However, the mechanism of coordination environment of metal catalytic centers in CO 2 adsorption and the selectivity of intermediates and products remains unclear. Herein, two N‐doped carbon nanosheets hosting coordination‐engineered Cu single atom (referred to as Cu‐N x , where x denotes the number of coordinated N atoms, e.g., Cu‐N 3 and Cu‐N 4 ) were synthesized via a simple two‐step pyrolysis process. The Cu‐N coordination number decreases with increasing pyrolysis temperature. Under visible light irradiation, the optimal catalyst with Cu‐N 3 coordination achieves a CH 4 yield of 219 µmol in 10 h using 5 mg catalyst with a selectivity of 97% in the presence of photosensitizer. In contrast, the high‐coordinated Cu‐N 4 site dominated catalyst exhibits a significantly lower CH 4 yield (58 µmol) and selectivity (93.7%), highlighting the advantage of the Cu‐N 3 motif for efficient CH 4 production. Experimental and theoretical results reveal that low‐coordinated Cu‐N 3 site favors * CHO intermediate via * CO hydrogenation (ΔG = 0.71 eV) rather than * CO desorption (ΔG = 0.83 eV), thereby promoting the selective CH 4 generation during the CO 2 photoreduction. In addition, the Cu‐N 3 coordination enhances CO 2 adsorption and charge transfer from Cu to CO 2 compared to Cu‐N 4 coordination. This work underscores the critical role of atomic‐level coordination engineering in optimizing the catalytic performance of single atom catalysts for efficient and selective solar fuel production.